A common requirement in spectrochemical analysis with inductively coupled or microwave induced plasma torches is to analyse liquid samples having relatively high concentrations of dissolved solids. In extreme cases the concentrations of such samples might approach the saturation point of one of the dissolved components. Liquid samples are usually introduced a plasma torch as aerosols produced by a nebulizer. Attempts to analyse highly concentrated samples can result in salts coming out of solution as the nebulised aerosol is generated and as it is transported through the torch. Salt particles are often deposited in the nebulizer or in the torch, ultimately causing blockages that require the analysis to be stopped and the apparatus to be disassembled and cleaned. This wastes valuable time. Nebulisers that are resistant to obstruction by salts are known in the art, but obstruction of the plasma torch has continued to cause difficulty.
An object of the present invention is to provide a torch for producing a plasma for use in spectrochemical analysis that is resistant to obstruction by salts deposited from samples containing high levels of dissolved solids.